SNOHOMISH — The health of Blackman Lake, once considered a jewel of the town, is continuing to decline because of a multitude of reasons.
The City Council is interested in pursuing an Algae Control Plan, a deep study of the best strategies for remedying recurring algae. County lake health officials advocated for the suggestion last week when visiting the council meeting.
It will cost a $25,000 match from the city coffers to do it, plus obtaining a $50,000 state Department of Ecology grant.
Council members spoke favorably to the idea. It’s possible the city will put it in its 2023-2024 biennial budget; some council members wondered if the city could act quicker.
The crux of what’s harming Blackman Lake is it has too much phosphorous, which robs the water of oxygen.
It comes by way of goose droppings, fertilizer runoff and pet feces.
This nutrient helps algae thrive, including algae containing bacteria that is toxic to people and pets. The lake just last week was being monitored for its latest algae bloom. These blooms have been getting more frequent, too.
The lake’s health has been declining for 30 years, data shows.
What phosphorous washes in, it doesn’t quickly wash out through circulation. It often settles into the lake, Snohomish County Surface Water Management Water Quality Specialist Marisa Burghdoff explained to the Tribune earlier this year.
In addition, Blackman Lake has two invasive plants that are difficult to control, lake health officials said last week. One are fragrant water lilies, which are colored white and pink unlike native lilies in the lake. The other is a newcomer: curly-leaf pondweed, a stringy plant that forms thick mats if left untreated. Lake monitors spotted the pondweed just this August near the boat launch.
Decomposing lilies add to unwanted silt to the bottom, causing the lake to slowly get shallower.
The pondweed will be tackled during 2022, County Water Quality Analyst Katie Ruthenberg told the council last week.
There are ways the public can help. For one, stores sell phosphorous-free fertilizers made by major name brands which people can choose to use. Secondly, picking up after pet waste prevents it from diluting into streams which feed lakes.
The city acted to dissuade geese before. They added a five-foot buffer of salal shrubs and similar native plants along the lakefront to make the area unfavorable to geese. Lakeside residents could add similar shrubs, county lake health officials said last week.
Separately, blue-green toxic algae sometimes looks like a paint spill on the water. Non-toxic algae looks like a mat.
You can report a bloom at www.nwtoxicalgae.org
